Category: natural selection

More misguided critique of the modern theory of evolution—in Skeptic magazine

July 6, 2026 • 9:00 am

A recent Skeptic magazine features George Levine’s review of a new book by Jessica Riskin: The Power of Life: The Invention of Biology and the Revolutionary Science of Jean-Baptiste Lamarck. It’s about the life and accomplishments of Jean-Baptiste Lamarck (1744-1829), one of the first naturalists to suggest that life evolved from earlier (and simpler) ancestors, and by natural processes.

Biologists largely know Lamarck from his having been wrong. Yes, organisms did evolve, but Lamarck got what drove evolution completely wrong. Instead of the better-adapted individuals in a species leaving more offspring, which was Darwin’s theory, Lamarck posited that evolution proceeded by two means:

a.) A teleological drive in organisms to become more complex, and

b.) Via the inheritance of acquired traits. That is, organisms somehow became more adapted to the environment through their own activities, and these acquired adaptations were passed on to the next generation. The classic example Lamarck gave—and one now used to debunk him—is his scenario of how giraffe’s got long necks. Originally, he said, giraffes had shorter necks, and had to stretch their necks to reach leaves higher up on trees.  That stretching made their necks longer, and, as this process continued over generations, giraffes got their astoundingly long neck. Their striving to reach leaves had somehow become inherited.

We know now that Lamarck was wrong on both counts. First, there is no teleological “drive” to become more complex (nor do all lineages become more complex: tapeworms, for example, lost nearly all their organ systems). Further, acquired traits are not inherited. Although Darwin mentioned that briefly, his alternative theory of natural selection (see below) was pretty much on the mark.  New suggestions that epigenetically acquired modifications become inherited fail on two counts: they are erased from the genome in a few generations, and they do not lead to adaptations. In fact, as in the case of the “Dutch Hunger Winter” of 1944-1945, epigenetic modifications of the DNA acted in a way that was maladaptive, raising the incidence of disease among descendants. Eventually, those environmentally-induced epigenetic changes in DNA disappear, as they always do when epigenetic modification is not itself coded by the DNA.

In the end, Lamark’s “theory” of evolution came to nothing and his work was largely ignored.  According to the Skeptic article by George Levine, Riskin’s book tries to rehabilitate the ignored Frenchman, arguing that Lamarck and Darwin were both right in some ways and wrong in others, with Lamarck making seminal contributions to biology.  But anybody who knows the history of evolutionary biology must realized Darwin was more right than Lamarck—by far—and it’s a stretch to even say that Lamarck made any big contributions to modern biology.

I have not yet read Riskin’s book, but I can say that Levine’s comparison of Darwin with Lamarck is deeply misguided. If he’s characterizing the book accurately—and I don’t know if he is—then the book is also misguided. But I don’t want to criticize Riskin. Rather, I want to correct the errors purveyed by Levine’s review. Click the title below to see that review.

First here’s Levine’s short bio from Skeptic:

George Levine is the author of Darwin and the Novelists (Harvard University Press/Chicago University Press); Darwin Loves You (Princeton University Press); and Darwin the Writer (Oxford University Press). He was a longtime professor at Rutgers University until his retirement in 2006.

Let’s take Levin’s major points (and errors) one by one.

a.) Where Darwin and Lamarck were both right.

Both of them suggested that evolution occurred by naturalistic means.  But while Lamarck’s ideas never caught on, Darwin’s did: within a decade after he published On the Origin of Species in 1859, most biologists and many educated people embraced Darwin’s main theories (see below).

b.) Where Darwin and Lamarck were both wrong, and how they differed in wrongness.

Neither Darwin nor Lamarck understood how heredity worked, and both suggested that acquired changes could be inherited.  While Lamarck suggested that use of an organ of feature changed the physiology of an organism in a way that could be inherited, he didn’t specify how.  Unlike Lamarck, Darwin did not see the inheritance of acquired traits as the only or the overweening method of evolutionary change, though he did posit a mechanism: organs and other bodily parts transmitted their changes to the reproductive organs through the production of small “gemmules” that somehow made their way to the reproductive organs. Darwin’s theory is called pangenesis, and was also wrong. The inheritance of acquired traits as a means of adaptive change has been disproven by many experiments. As I’ve written in detail, epigenetic modification of the DNA by environmental change is not a mechanism of adaptive evolution.

Although both men were wrong about acquired traits changing inheritance for good, Lamarck was also wrong by positing a teleological process that, over time, drove species to become more complex.

c.) Why Darwin is revered and Lamarck ignored.

While Levine spends a lot of time arguing that Lamarck and Darwin were both wrong, and yet both made seminal contributions to biology, he largely ignores the reason why Darwin is lauded and Lamarck is ignored   There are two reasons for this:

1.) Darwin provided copious evidence for evolution and against creationism, and Lamarck did not. If you read The Origin, you will find chapter after chapter detailing evidence for why evolution was correct and Biblical creationism was not.  Darwin describes how features of development, vestigial organs, biogeography, and even the fossil record (very sketchy in Darwin’s time) militate against creationism and in favor of evolution. In this way, Darwin shoved aside the dominant theory of how life came to be in favor of a naturalistic theory driven by what he saw as his greatest idea, #2:

2.) Darwin was the first to suggest a plausible mechanism for evolution supported by evidence: natural selection. Lamarck’s mechanism was not plausible. The idea of natural selection is the theory that organisms with traits that made them more adapted to the environment left more offspring—and, if trait variation was heritable (as it usually is), enriched the next generation with more adaptations—was Darwin’s greatest contribution to biology. While the idea of evolution was “in the air” in the mid-19th century, if Darwin hadn’t come up with natural selection, the modern theory of evolution would have been delayed by decades.  Although Darwin did see “pangenesis” as one mechanism of evolution, another was the (correct) idea that individuals in a species were different from another and those differences were largely due to differences in their hereditary material.  Darwin proposed that these differences could be due to “mutations” coming from environmental changes. Though that wasn’t correct (mutations appear to be random), environmental causation isn’t necessary for natural selection to work. All we need to know is that something causes individuals to differ in their traits, and some of those differences could be inherited. That, combined with the idea that trait differences could affect reproduction, is all ye need to know.

Darwin supported this idea simply by drawing a parallel with artificial selection, which, as Darwin’s own experiments with pigeons showed, was hugely successful in modifying species in any direction the breeder wanted.  The importance of this argument is shown by Darwin’s devoting the first chapter of The Origin to it: “Variation Under Domestication.” My favorite quote in this chapter is this:

Breeders habitually speak of an animals’ organisation as something quite plastic, which they can model almost as they please.”

It works for plants, too, of course, as we know from almost all our domestic crops being extreme modifications of species found in nature, all effected by artificial selection.

The parallel is nearly exact, save that the breeder determines which traits are adaptive, while it happens by itself in nature. But in both cases more-adapted individuals leave more offspring, transforming the species. The argument is very convincing, and natural selection transforming species has now been demonstrated many times in nature. You don’t need a human breeder.

Darwin, then, is most revered for the twin achievements of demonstrating the truth of evolution and then providing a plausible mechanism for the production of “the endless forms most beautiful and most wonderful” limned in the last paragraph of The Origin. Lamarck did neither of these things.

d.) So what were Lamarch’s contributions to modern biology?  Levine mentions three.  “Lamarck was the first to use the word ‘biology’ and to conceive biology as a separate science.” And he “invented the category ‘vertebrates’, separating them off from ‘invertebrates’ in scientific study.” That’s about it, and it doesn’t even come close to what Darwin accomplished.  Besides, in many cases it’s not useful to separate vertebrates from invertebrates. Often we want to study phenomena seen in both groups.

e.) Levine’s  review has a lot of misconceptions about Lamarck.  For some reason that baffles me, Levine thinks that Lamarck contributed to modern biology the idea that, via their own behaviors, organisms can change how natural selection acts on them.  Lamarck, he said, added to modern biology the idea that agents are not just passive “victims” of natural selection imposed from without by the environment, but can promote their own evolution through their behavior.  Beavers, for example, evolved to build dams, and by evolving that behavior they made themselves subject to whole new areas of natural selection: finding the right places to build, developing sharper teeth and behaviors to gnaw down trees, and turning their dams into homes.

But that idea—that organisms can promote their further evolution through behavior—while correct, was not contributed by Lamarck. It’s a well-established part of the modern theory of evolution called niche construction. It was implied even by Darwin, who wrote in his book on earthworms that they modify their environments. But it was brought into evolutionary biology by my own advisor, Dick Lewontin, and then made more formal by John Odling-Smee and Mark Feldman.  Lamarck had nothing to do with this addition to the modern synthetic theory of evolution.

In fact, Levine goes even further, and jumps the rails when he seems to suggest that organisms want to evolve in certain directions, a view that borders on Lamarck’s teleology. (Bolding is mine,)

Natural selection and Lamarckian evolution are not necessarily incompatible theories. Riskin points out that in 1896, James Mark Baldwin published a paper called “Organic Selection,” which, after first being contested ferociously “had recently achieved widespread acceptance among biologists.” “Organic Selection means selection that an organism enacts upon itself by behaving in certain ways.” For example, once humans found that opposable thumbs could help in survival, natural selection did its work and those born with opposable thumbs had a greater chance to survive. In this case, natural selection and something like Lamarckian intention co-exist. In fact, they depend upon each other. Human desire and intention change what it is to adapt. So, as Riskin puts it, “organisms aren’t just the passive objects of natural selection but its active conductors.” Hey, that might be a way to make Lamarck’s poor abused giraffes respectable.

For Lamarck, via Riskin, organisms are active in their own adaptiveness. They are capable of changing the environment to make it compatible with their needs. And here Riskin introduced me to a powerful and crucial element of Lamarckism that we have all ignored to our peril: Organisms are capable of changing their own environments. Usually, they do it in what they take to be their own interest. As we have all too slowly become aware, we have been working toward a new era: after the Pleistocene has come the Holocene and now (though still disputed) the Anthropocene—the era “defined by significant human impact on Earth’s geology, climate, and ecosystems.”

How can we hack our way through this weedy patch of misunderstanding? First, how did humans get opposable thumbs in the first place, if not through natural selection? Did a hominim with a mutant thumb appear one day, observe it had opposable thumbs, and then say, “I must evolve in this way.” That sounds dumb, but here Levine has got the cause and effect reversed. Natural selection did its work on the ancestral hominin hand to form opposable thumbs which, as time passed, became stronger and more dextrous (we know this from the fossil record).  What does “intention” have to do with this? Nothing, as far as I can see. Nor can organisms evolve via “what they take to be their own interest.”  Natural selection has nothing to do with the “self interest’ of organisms, most of which don’t even have “self-interest”.  Yes, organisms can behave in ways that suit them, and that can lead to new selective pressures, as with beavers and earthworms, but “interest’ has nothing to do with it.  This idea borders on teleological, as it is in the wacky new “Third Way” of evolution, which also has teleological elements,

f.) As if this weren’t bad enough, Levine tars the modern theory of evolution by connecting it with eugenics and environmental despoliation. It’s another way of praising Lamarck because his theory wasn’t in any way connected with this bad stuff.  Levine says this:

One depressing and horrifying fact of which Riskin has made me aware is that just about every major figure in the development of the “modern synthesis” was a eugenicist. Clearly, this is no accident. Humans, from the perspective behind the Weismann barrier, are objects to be manipulated, coal mines to be dug out. Bad gene clusters to be eliminated. It is partly as a polemic against this view of the absence of agency in this world that Riskin devotes the later part of her book. But it never takes the shape of polemic.

. . . What Riskin shows is that for Lamarck the kind of thinking implicit in the modern synthesis was and remains a moral and physical disaster.

It’s a physical disaster presumably because Lamarck pointed out that humans were destroying the environment and Darwin didn’t. But again, this has nothing to do with Darwin’s theory, nor does it show that Darwin was “wrong. ”  Connecting Darwinism with eugenics and environmental depredation is the final error in a string of misconceptions and outright errors by Levine. Pity that this stuff was published in Skeptic magazine, which apparently didn’t get Levine’s review vetted by an evolutionary biologist. I emphasize again that because I haven’t read Riskin’s book, my criticisms are directed not at her but at the reviewer.

Beauty is in the (evolved) eye of the beholder

May 18, 2026 • 9:45 am

Right now I’m reading Steve Stewart-Williams’s new book: A Billion Years of Sex Differences: How Evolution Shaped the Minds of Men and Women. It is neither a pure blank-slate social-constructivist book nor a hereditarian, genetic-deterministic book, but takes an evidence-based middle ground, asking to what extent behaviors and mindset are molded by evolution and to what extent social conditioning plays a role.  I won’t give a take on the book as I’m not yet finished, but it does make many arguments I’m familiar with.  One of these is the familiar and well-documented claim that, based on different degrees of parental investment, men concentrate more than women on beauty when looking for a mate, while women are less interested in appearance than are men but more interested in paternal behavior, status, and wealth of a prospective mate. These are not absolute differences, of course: many men want women who will invest a lot in their offspring (we are, after all, generally monogamous), and many women want men who are pleasing to the eye. This is a difference in average preferences, not absolute ones characterizing all individuals.

Although some of this average sex difference in behavior may reflect social conditioning, its evolutionary background is likely based in part on the differential investment between the sexes in offspring: although many societies are polyandrous and monogamous, on average males still have a potentially larger number of offspring than do females. This appears to be true in many societies, as well as in our closest relatives, the apes and in most species of animals. Women, who by virtue of their reproduction (as well as by both the evolutionary and social impetus to do most of the childcare) need fathers who will do their share of parental duties and provide for the offspring.  And of course men do share some of those duties, but are also more interested in casual sex and adultery—a way to spread more of their genes when they don’t invest as much in offspring.

If you want the evidence for this, read Stewart-Williams’s book or the references he cites.

Why am I pondering this? Because when I went to the library the other day, I caught a glimpse of myself in the entry door and thought, “Geez, look at that ugly old man!”  Whatever attractive physical features I once had—and I was never close to being a Robert Redford—have vanished, carried away by time’s wingéd chariot.  Women, too, worry about ageing, and are even more concerned about it because of a key difference between men and women: as women get older and become unable to reproduce, they become less desirable faster than do men.  A man can have offspring even in his eighties, while in their early fifties most women hit menopause, which means no more kids. Since men have largely evolved to be physically attracted to women who can give them children, women try harder than do men to retain the signs of youth: hair color, plastic surgery, botox, and the like. On average, they try harder to retain physical attractiveness because it is that rather than status that is a dominant way of attracting partners—and most people want a partner.

Which brings up a tangential point: what about gay men and women?  I don’t know their preferences but it would be interesting to study (and I’m sure people have) whether men attracted to other men for lasting partnerships are less concerned with looks than are women attracted to other women for partnerships.

Back to the point, which is this. It is my theory, which is mine (and likely many other people’s) that there is really no objective difference in physical attractiveness with age, in either men or women.  Old men and women look different from their younger selves (I now refrain from looking in mirrors), but the beauty associated with youth and the loss in attractiveness associated with age are not anything objective (beauty never is, of course).  We are simply evolved to think that those features associated with having more offspring on us are more “beautiful”, as those mindsets are the ones promoted by natural selection. This explains why women are more concerned with the physical ravages of time then are men, for their physical attractiveness to the other sex wanes faster with time. I’ve often heard older actresses say that by the time they hit forty, Hollywood no longer wants them, while that doesn’t happen so much with male actors.  Why is this difference retained past the age of reproduction in women? I suppose it’s because it’s largely innate and most women didn’t live past menopause during most of our evolution.

Thus beauty is in the eye of the beholder: it is subjective, like all standards of beauty, but the subjectivity is molded in certain directions by natural selection.

I am not, of course, saying that this is good—only that much of it is natural. I do not want to commit the naturalistic fallacy here, but simply consider what aspects of our minds and behaviors might be based on genes, to what extent, and whether those evolutionary bits have been molded by natural selection.

This parallels a point I’ve made before: other aspects of our senses, like tastes, are clearly molded by natural selection.  I have said, for example, that to a vulture rotten meat tastes as good as an ice-cream sundae does to us.  Animals have evolved to search for food that tastes good because, over time, our senses evolve to find the food we need to grow and reproduce to be tasty. In other words, natural selextion has molded our taste buds and our brains so we prefer what is nutritious and fosters reproduction.  This can be hijacked: we now eat too many fats and sweets because those substances were desirable to our ancestors as they were rare but promoted reproduction.  Now they no longer do so because of the surfeit of “bad” food on tap.  But our taste buds haven’t yet caught up to our health.

Why do feces and vomit repel us, smelling foul? It’s very likely that these substances were evolutionarily associated with the spread of disease, and so we evolved smell-detectors that find them repugnant. After all, dung beetles love the odor of feces!

I’ll draw one more parallel here. Anybody who thinks about it seriously must admit that male orgasms, intricate and immensely pleasurable physiological mechanisms associated with ejaculation, have evolved as a way of promoting reproduction (the evolutionary basis of female orgasms is more speculative, but there is no shortage of adaptive hypotheses).  Orgasms are a way of getting men to produce offspring, just as sweetness is a way of getting us to eat sugar. And, like eating too many sweets, orgasms can be hijacked—severed from their reproductive function by condoms, chemicals, or medication. Organizations like the Catholic Church have tried mightily to try to reconnect sex and reproduction, but it is largely in vain.

I have undoubtedly written this too fast, as I just had some thoughts and wanted to get them down on paper before I forget them. I’ve considered that I’m trying to dispel my idea that I’m unattractive, and in so doing thought about physical attraction in general. And yes, I’m also reading Stewart-Williams’s book, which considers in detail this and other aspects of human (and animal) mentation and behavior.

Once you get an evolutionary mindset, all sorts of behaviors now become more interesting. That doesn’t mean we should make up adaptive stories and consider those stories to be true, but neither should we ignore possible evolutionary explanations. To explain the evolutionary basis of human behaviors and minds will be hard, as most of them evolved in the unrecoverable distant past—in our ancestors.  But some of the explanations are testable, and here I must stop.

On the origin of venom by means of natural selection

December 11, 2025 • 10:20 am

Many animals are venomous, but in most cases the exact proteins involved in causing pain or death are unknown, and even in those cases the genes producing them have not been identified, counted or mapped.  If you’re interested in the evolution of venom, what its precursors are, and how venomous animals avoid poisoning themselves, you have to know this kind of stuff.

A new paper in Proc. Nat. Acad. Sciences (click screenshot below to read for free, or find the pdf here) answered several of these questions in the venomous caterpillar of the mottled cup moth (Doratifera vulnerans), shown below.  It’s from Australia, and is described in Wikipedia this way:

It is known for its caterpillar having unique stinging spines or hairs that contain toxins, for which the scientific name is given that means “bearer of gifts of wounds”. Chemical and genetic analysis in 2021 show that its caterpillar contains 151 toxins, some of which have medicinal properties

That earlier paper, from 2021 and including some of the same authors as the one we discuss today, did indeed identify 151 proteins (peptide are bits of proteins or short chains of amino acids) that were in the toxins, but did not know which genes produced them, how the genes were arranged, what the closest relatives of the genes were, and how many of the 151 “toxins” were really toxic (the word “toxin” there and in the present paper do not mean that the substances were toxic, but that they were simply a component of the extracted toxins). However, the authors, some on the paper I’m highlighting today, did identify two genuine toxins that caused pain: the peptides Dv12 and Dv11.

Look at this thing! It’s clearly aposematic, meaning that it has bright warning coloration that predators can recognize and learn to avoid. And you can see those nasty spines.  In the earlier paper they extracted toxins from related species and tested them by injecting them into mice tails, guinea pigs, and human volunteers. That earlier paper also adds this about the species name:

This species, whose binomial name etymologically means “bearer of painful gifts,” is a common culprit of caterpillar envenomations in Australia.

That means that many Aussies get stung by these things, probably inadvertently. Would you touch an animal that looks like this?:

Photo by Fir0002,  Creative Commons Attribution-Share Alike 3.0 Unported license.

On to the new paper, and I’ll try to be brief as it’s long and complicated.

1.) First, the authors sequenced the entire caterpillar genome (remember, it’s the same as the adult moth genome).

2.) Then, knowing the sequences of the proteins known from previous work on toxins, they could find the genes producing them by matching the protein sequence to the DNA sequence that could produce these proteins. Of the 151 proteins in caterpillar venom known from the prvious work, they mapped 149 of them to 115 sites in the genome

3.) Of the 115 sites, 35 were products of single genes, while 80 (70%) of the total, were members of gene families consisting of two or more similar genes (sometimes many genes) with similar sequences.  Here’s a map of the “toxin gene” locations on the insect’s 13 chromosomes. The blue dots are the genes existing in single copies, orange dots are clusters of genes previously grouped together by protein-sequence similarity, and pink dots are genes that were newly identified, surely as part of gene families, in the present study. This conclusion comes from their sequence similarity and they physical grouping on two chromosomes.(The size of the dots indicates the number of genes that are part of a contiguous group. Click to enlarge:

So we know that genes found in venom are very often the product of gene duplications, either of single genes becoming two (this can happen via unequal crossing-over during meiosis or by other methods), producing two initially identical genes side by side or whole groups of them (“tandem duplications”). Once a gene has been duplicated, the original copy can then keep its original function, while the other copies, not being “needed,” are free to evolve other functions. Many genes we’re familiar with, like our own globins and immunoglobulins, evolved by gene duplication followed by divergence of the duplicated copies.

Where did the genes making venom proteins come from? This is the key evolutionary question answered here and, to some extent, in the previous paper. They evolved from ancestral genes in the moth’s immune system that evolved to attack microbes, the so-called “antimicrobial peptides” (AMPs), also known as cecropins. The ancestral AMP proteins, nearly identical to their original form and function, kill bacteria (prokaryotes) by disrupting the bacterial membranes. Insects still need to kill microbes!

Clearly, the proteins in venom have evolved by natural selection modifying ancestral genes used to kill bacteria. Now they are used to repel predators. Natural selection causing this divergence was implicated by looking at sequence differences, as there are ways of showing what sequence differences evolve faster than expected under either the slower processes of genetic drift or “purifying” selection that conserves structure.  They found that most of the venom-adapted proteins that evolved from cecropins did evolve under natural selection, while the descendants of cecropins that retained their original anti-microbial proteins were under purifying selection to retain their sequence. It’s clear, then, that the insect still needs genes to attack bacteria. It’s just that some of them have been repurposed, often through gene duplication and divergence, to repel predators. (The authors have a way of assessing “pain” by measuring the increase in calcium concentration in cells grown in vitro and exposed to venom. This happens when the two investigated proteins are used.)

Here is a complicated family tree of cecropin genes in black used to kill microbes. The genes found in venom are in the red box (“venom adapted”). You can see that they are related to cecropin genes but branched off fairly recently (probably four or five million years ago). The venom genes are in the red box that I’ve added, and their relationship as being derived from ancestral AMP genes is very clear. (The “canonical” genes in green are antimicrobial proteins closely related in sequence to the venom genes.

So, now we know where the genes in venom come from. What we do not know is how many of those genes are essential in venom, either causing pain or doing other stuff that venom needs to do. At least two of them cause pain, but there are probably more, for they haven’t all been tested. And some of the other genes are probably involved in dismantling cell walls in potential predators. The authors tested several of the venom proteins and also found that, as in their AMP ancestors, they disrupt cell covering, in this case eukaryotic cell membranes.

Finally, the big question: If the caterpillar makes venom, why doesn’t it poison itself? Here’s how the authors answer that question (I’ve put the answer for this species is in bold).

Animals that produce toxins, either for innate immunity or as venom toxins, must employ strategies to protect themselves from toxicity. Such protective mechanisms include production of toxin inhibitors, storage in inactive form, mutations in their own ion channels that confer resistance, alteration of lipid bilayer compositions, and compartmentalization of toxins separate from body tissues. In the case of limacodid venom peptides, the venom is compartmentalized into the cuticle-lined venom reservoir inside venom spines, preventing the toxin from coming into contact with cells other than the secretory cells that produce them. Thus, compared to canonical cecropins, venom-adapted cecropins may also be released from pressure to avoid activity against animal cells.

There are other findings in the paper that will be of interest primarily to those studying genomic evolution. For example, many of the venom proteins still retain some weak antimicrobial activity, so the idea that genes completely lose their ancestral function when they gain a new one doesn’t hold in this case.

Below you can see the adult moth because, remember, they studied caterpillar venoms, and many of those genes are probably turned off in the adult. But adult and caterpillar carry the exact same genes, of course; their different bodies, physiology, and behavior rest on the differential turning on and off of these genes at different life stages. And that remains a big mystery: how do such different life stages evolve, with each step of the evolution being adaptive?

From The Australian Museum, photo credits at bottom (click to enlarge), image by Lyn Craggs.

 

Michael Lynch takes apart two attempts to forge new evolutionary “laws”

June 13, 2025 • 10:00 am

Biology isn’t really like physics: we don’t have “laws” that are always obeyed, but instead have generalizations, some of which hold across nearly organisms (but even the “law” that organisms have DNA as their genetic material is flouted). The only “law” I can think of is really a syllogism that Darwin used to show natural selection: a). if there is genetic variation among individuals for a trait, and b). if carriers of some of the variants leaves more copies of their genes for the trait than carriers of other variants, then c). those genes will be overrepresented in future generations, and the trait will change according to the effects of the overrepresented genes.

But even that is not a “law” but a syllogism. After all, natural selection doesn’t have to work.  There may be no genetic variation, as in organisms that are clonal, and different variants may not leave predictably different copies of themselves in future generations; such variants are called “neutral”.  So there is no “law” that natural selection has to change organisms.

In this paper (click on screenshot below, or find the pdf here), evolutionary geneticist Michael Lynch from Arizona State University goes after two papers (cited at bottom of this post) that, he says, are not only failed attempts to concoct “laws” of evolution, but are flat wrong because their proponents don’t know squat about evolutionary biology.  I’ll try to be very brief because the arguments are complex, and unless you know Lynch’s work on the neutral theory, much of the paper is a tough slog.  What is fun about the paper, though is that Lynch doesn’t pull any punches, saying outright that the authors don’t know what they’re doing.

Here’s the abstract followed by an early part of the paper, just to show you what Lynch is doing. Bolding is mine:

Abstract:  Recent papers by physicists, chemists, and geologists lay claim to the discovery of new principles of evolution that have somehow eluded over a century of work by evolutionary biologists, going so far as to elevate their ideas to the same stature as the fundamental laws of physics. These claims have been made in the apparent absence of any awareness of the theoretical framework of evolutionary biology that has existed for decades. The numerical indices being promoted suffer from numerous conceptual and quantitative problems, to the point of being devoid of meaning, with the authors even failing to recognize the distinction between mutation and selection. Moreover, the promulgators of these new laws base their arguments on the idea that natural selection is in relentless pursuit of increasing organismal complexity, despite the absence of any evidence in support of this and plenty pointing in the opposite direction. Evolutionary biology embraces interdisciplinary thinking, but there is no fundamental reason why the field of evolution should be subject to levels of unsubstantiated speculation that would be unacceptable in any other area of science.

. . . we are now living in a new kind of world. Successful politicians and flamboyant preachers routinely focus on the development of false narratives, also known as alternative facts, repeating them enough times to convince the naive that the new message is the absolute truth. This strategy is remarkably similar to earnest attempts by outsiders to redefine the field of evolutionary theory, typically proclaiming the latter to be in a state of woeful ignorance, while exhibiting little interest in learning what the field is actually about. Intelligent designers insist that molecular biology is too complex to have evolved by earthly evolutionary processes. A small but vocal group of proselytizers clamoring for an “extended evolutionary synthesis” continues to argue that a revolution will come once a critical mass of disciples is recruited (7–9), even though virtually every point identified as ignored has been thoroughly evaluated in prior research; see table 1.1 in ref. 6. More than one physicist has claimed that all of biology is simply physics. But 2023 marked a new level of advocacy by a small group of physicists, chemists, and geologists to rescue the field of evolutionary science from obfuscation, and to do so by introducing new theories and laws said to have grand unifying potential.

Note Lynch’s criticism of the “Extended Evolutionary Synthesis”, a program (and associated group of investigators) who claim revolutionary ways of looking at evolution, which, as Lynch notes, have already been discussed under conventional neo-Darwinian theory.

There are two theories Lynch criticizes in this paper

1.) Assembly theory. This is the complicated bit from the paper of Sharma et al. (see references below). It involves an equation that supposedly gives a threshold beyond which the assembly of components indicates life that evolved via natural selection (I won’t define the components, either, which aren’t important for the general reader’s purpose:

According to Walsh, this equation is totally bogus because it neglects all the forces that can impinge on gene forms during evolution. An excerpt:

However, this is not the biggest problem with assembly theory and its proposed utility in revealing the mechanistic origins of molecular mixtures. A second, more fundamental issue is that the authors repeatedly misuse the term selection, failing to realize that, even in its simplest form, evolution is a joint function of mutation bias, natural selection, and the power of random drift. There is a fundamental distinction between the mutational processes that give rise to an object and the ability of selection (natural or otherwise) to subsequently promote (or eradicate) it. In the field of evolution, drift refers to the collective influences of stochastic factors governed by universal factors such as finite population size, variation in family sizes, and background interference induced by the simultaneous presence of multiple mutations; via the generation of noise, the magnitude of drift modulates the efficiency of selection. For the past century, these processes have been the central components of evolutionary theory (reviewed in refs. 5 and 6).

Because this theory neglects forces like mutation and genetic drift that can change frequencies of gene forms beyond natural selection, Lynch deems it “a meaningless measure of the origins of complexity.”

2.) The notion that organismal complexity is an inevitable result of natural selection. This goes after the paper of Wong et al., and you should already know that this can’t be true: evolution is not, in any lineage, a march towards more and more complex species. The immediate refutation is the existence of parasites like fleas and tapeworms, which have lost many of their features to pursue a parasitic lifestyle.  If you make your living by parasitizing other organisms, natural selection can actually favor the loss of complexity. Tapeworms, for example, have lost many of their sensory systems, their digestive system, and features of their reproductive system.  By any measure of complexity, they are much simpler than their flatworm ancestors.

Lynch points this out, and adds that there are lineages of microbes (very simple one-celled organisms like bacteria) that have not become more complex over the billions of years they existed. There may have been a burst of complexity when the lineages arose, but clearly bacteria haven’t been on a one-way march to primates. They are doing a fine job as they are:

Despite their substantially more complex ribosomes and mechanisms for assembling them, eukaryotes do not have elevated rates or improved accuracies of translation, and if anything, catalytic rates and degrees of enzyme accuracy are reduced relative to those in prokaryotes (with simpler homomeric enzymes). Eukaryotes have diminished bioenergetic capacities (i.e., growth rates) relative to prokaryotes (21, 22), and this reduction is particularly pronounced in multicellular species (23). Finally, it is worth noting that numerous organisms (parasites in particular, which constitute a large fraction of organisms) typically evolve simplified genomes, and many biosynthetic pathways for amino acids and cofactors have been lost in the metazoan lineage.

Another bit of evidence against Wong et al. is that their adducing “subfunctionalization”, whereby genes duplicate and the duplicate copies assume new functions, shows some “law” of increasing complexity. (The divergence of hemoglobins occurred in this way.) But Lynch suggests that genes don’t duplicate to make an organism more complex, and, moreover, the differential functions of duplicate genes can arise from selection being relaxed:

Subfunctionalization does not arise because natural selection is striving for such an endpoint, which is an energetic and a mutational burden, but because of the relaxed efficiency of selection in lineages of organisms with reduced effective population sizes. How then does one relate gene number to functional information?

Lynch winds up excoriating these new “theories” again:

For authors confident enough to postulate a new law of evolution, surely some methodology and supportive data could have been provided. Science is littered with historical fads that became transiently fashionable, only to fade into the background, with a nugget of potential importance sometimes remaining (e.g., concepts derived from chaos theory, concerted evolution, evolvability, fractals, network science, and robustness). But usually when the latter happens, there is a clear starting point. This is not the case with the “law of increasing functional information,” which fails to even provide useful definitions of function and information.

. . . . To sum up, all evidence suggests that expansions in genomic and molecular complexity, largely restricted to just a small number of lineages (one including us humans), are not responses to adaptive processes. Instead, the embellishments of cellular complexity that arise in certain lineages are unavoidable consequences of a reduction in the efficiency of selection in organisms experiencing high levels of random genetic drift.

I would take issue only with Lynch’s claim that only a “small number of lineages” have become more complex than their ancestors.  Most multicellular organisms are this way.  In the end, though, Lynch’s lesson is that people should learn more about evolutionary theory, which has grown quite complex, before they start proposing “revolutionary laws of evolution.”

The two papers at issue (I’ve provided links.)

10. A. Sharma et al., Assembly theory explains and quantifies selection and evolution. Nature 622, 321–328 (2023).

11. M. L. Wong et al., On the roles of function and selection in evolving systems. Proc. Natl. Acad. Sci. U.S.A. 120, e2310223120 (2023). 

Possible evolution of hummingbird beaks since WWII

May 28, 2025 • 10:45 am

The report below may represent a case of rapid adaptive evolution of a trait: the beaks of Anna’s hummingbirds (Calypte anna) in California, though there are sufficient confounding factors that, were I teaching evolution, I would still use Peter and Rosemary Grant’s work on the beaks of medium ground finches in the Galápagos as my paradigm. (The Galápagos incident occurred over a single year on one small island and confounding factors are virtually nil).

First the species: a male Anna’s Hummingbird flying:

Robert McMorran, United States Fish and Wildlife Service, Public domainvia Wikimedia Commons

and a female hovering:

Mfield, Matthew Field, CC BY-SA 3.0 via Wikimedia Commons

Click below to read the article, and find the pdf here.

The authors posited that the increasing use of hummingbird feeders after WWII would select for changes in the bill length of this species because individuals who could reach and consume more nectar from newfangled feeders (which reward copious nectar swilling) would have a reproductive advantage. Their predictions were met, but there are complications.

Here’s a hummingbird feeder:

Centpacrr at English Wikipedia, CC BY-SA 3.0, via Wikimedia Commons

That’s a very common design, with the feeder filled with sweet liquid: often sugar water, which is okay but commercial nectar containing other nutritive substances is better. The paper describes the spread of feeders and the morphology of AH beaks over time, using about 400 museum specimens gathered since 1860. Feeders, though, were introduced mostly after WWII (from the paper):

Although it likely existed earlier, we report that the widespread recreational hummingbird feeding can be traced back to an article published in National Geographic in 1928 documenting how to ‘tame’ hummingbirds by making bottles of sweet liquid masquerading as flowers (Bodine 1928); this method is thought to have directly influenced the first patented hummingbird feeder in 1947 (True 1995). As a result of this newly popularized feeder, terms associated with hummingbird feeders in local newspapers increased rapidly from southern to northern California, where feeder density began its increase in the historic range accompanied by an increase of ANHU populations as they moved north.

Based on the spread of hummingbird feeders, the authors posited an evolutionary change in beak shape (remember, this is over 80 years):

We therefore expect feeders to select for increased volume with each lick resulting from increased bill length and thickness. In feeders, unlike flowers, nectar pools are not quickly depleted and therefore the short distance between the bill tip and the nectar surface remains relatively constant, such that minimizing the bill-nectar gap allows higher licking rates and extraction efficiency (Kingsolver and Daniel 1983; Rico-Guevara et al. 2015; Rico-Guevara and Rubega 2011; Kingsolver and Daniel 1983).

“Minimizing the bill-nectar gap” involves evolving longer bills. And getting more capacious bills allows you to take in more nectar in one slurp.

And this is what they found.  First, though, there are quite a few confounding factors that the authors had to consider:

  • Eucalyptus trees, an invasive species and also a source of food for Anna’s Hummingbird (called AH in this post), also spread over that period
  • Humans also spread, and urbanization spread from southern to northern California, so there is a climatic factor to consider, too. Since bills are a source of heat loss, we expect birds in colder climate sin the north to have shorter bills (and they did indeed find this)
  • Feeders could have a secondary effect by promoting fights between males, who try to monopolize the “nectar” source. It could be this fighting that would select for changes in bill shape, since bills are used in fighting. Attendant changes in female shape could simply be a byproduct of selection in males.
  • Increased urbanization itself could change beak shape, perhaps because it leads to planting of flowers that select for longer bills

Data analysis was done (this is above my pay grade) using a multivariate analysis, taking into account year, location, temperature, beak measurements, and the abundance of feeders and Eucalyptus trees. The latter two factors were estimated—not very satisfactorily—using newspaper mentions since 1880. The results were these:

  • The abundance of eucalyptus trees had a small effect on increasing bill length and thickness, but it was much smaller than. . . .
  • The density of feeders, which had a highly significant effect, increasing both bill length and thickness (bill dorsal area) in the predicted way
  • However, bill size was smaller in colder climates, representing a presumed tradeoff between acquiring nectar from feeders and conserving heat when it’s cold
  • Human population size and year also had strong effects, changing the trait in the expected direction, as one would expect if natural selection were causing evolution of bill size and shape over time
  • Feeder density had a stronger effect on population size of AHs in northern rather than southern California. From the paper:

We find that feeders and human population size are both strongly positively associated with ANHU [Anna’s Hummingbird] counts (Figure S9) and each appear to have facilitated population growth differently throughout California (Figure 1B,C). Specifically, feeder availability appears to have facilitated population growth at northern latitudes, whereas human population size appears to have contributed more strongly to population growth in ANHU’s native range in southern California. These findings corroborate work conducted by Greig et al. (2017) suggesting that hummingbirds at northern latitudes are more reliant on feeders in winter than those at southern latitudes, while ANHU population growth is supported by urbanized human environments.

Why urbanized environments select for higher hummingbird populations independently of feeders is a bit counterintuitive, but perhaps it has to do with planted gardens.

The upshot:  So, do we have an example of evolution by natural selection here, one based on the proliferation of feeders causing evolution in beak length and shape? It’s possible, but there are a lot of problems. They include a rather small sample size for a model with many covarying factors, the use of newspapers to estimate feeder and Eucalyptus density, an unexplained change in beak shape with feeder density (a constriction appears in the middle of the beak), and no solid evidence that the change is really genetic rather than a change in beak shape induced environmentally by the use of feeders.  (I’ll add, though, that increasing change in time suggests genetic evolution rather than a one-time environmental modification by using feeders.) But the Grants’ work had pretty strong evidence that the change in beak size in the Medium Ground Finch on Daphne Island was genetically based. (They did a heritability analysis.)

One way to test this hypothesis would be to take an area lacking many feeders, but having Anna’s Hummingbirds, and then saturate it with feeders (best to use commercial nectar). If you monitor the birds over a number of years, one should expect to see, in that one small area, a change in beak shape. But nobody is going to do this experiment, because they’d probably expire before it was done. The Grant’s experiment documented change in beak shape over just a single year, and is, to me, far more convincing.

The fantastic Alpine ibex, and some musings about the primacy of behavioral adaptation

January 27, 2025 • 12:15 pm

I’m feeling grotty today, probably because of dysthymia compounded by lack of sleep. I hope to be okay tomorrow, but in the meantime we have show and tell. The show and tell today involves the Alpine Ibex (Capra ibex), the subject of a nice seven-minute video.  It concentrates on their remarkable ability to climb on ledges that look unclimbable, something the many goat species can do as well.  The videos mentions that young goats must “overcome their fear,” but I wonder if they really feel fear.

Note the morphological traits that have evolved in concert with this behavior, including body shape. Surely the ability to climb (a behavioral trait) preceded the evolution of things like those split hooves with soft pads, supporting Ernst Mayr’s claim that many key adaptations begin not as changes in morphology, but changes in behavior that give a premium to later morphological evolution. I just opened a book that was perhaps the most influential volume of my career, Mayr’s 1963 Animal Species and Evolution. I found this sentence on p. 604:

“A shift into a new niche or adaptive zone is, almost without exception, initiated by a change in behavior.”

Mayr was a smart guy, and was probably right. The important question, though, is, though, “do those changes in behavior have a genetic basis“? It’s hard to see, for example, how a goat with a greater propensity to climb, but not one based on genetic differences from other individuals, could possibly kick off a bout of evolutionary change, for there would be no increase of climbing behavior unless it came with an adaptive advantage that could be passed on via genes.  If the first climbers did have genetic differences from non-climbers, and climbing resulted in more of your genes being passed on, you would get an increase in the behavior over time since it conferred a reproductive advantage. (This didn’t start with some individuals climbing sheer cliffs, of course!). After that, any mutations changing the hoof or body shape would be subject to natural selection.  In this case, simple behavioral variation not based on genes wouldn’t, I think, kick off behaviors and morphologies like those shown below.

I can think of one exception: the famous case of cultural evolution of milk-drinking in British birds, first noted by Fisher and Hinde in 1949 (they studied blue and great tits). This was apparently a case of cultural evolution, which started with one or a few individuals prying the tops off milk bottles left on doorsteps and drinking the cream. This spread rapidly throughout the UK, so rapidly that it must have been a spread via imitation—that is, cultural evolution, not genetic evolution. Of course that would be followed by natural selection leading to things like prying the caps off better (beak changes?), locating milk bottles more readily, and digesting the milk. I don’t think anybody has studied any subsequent evolution in the birds (for one thing, milk isn’t delivered on doorsteps any more!); but this is one case in which a potential change in an “adaptive zone”—however you describe it—began with a simple behavioral change not based on genetic differences.

Sorry, I was just thinking on paper. Watch the video, which is amazing and instructive:

ZeFrank on plants with explosive dispersal

July 1, 2024 • 12:20 pm

There’s a trigger warning on ZeFrank’s recent video: “True Facts is not appropriate for children, nor for adults who don’t act like children.” But in fact this 11+ minute video is perfectly appropriate for kids. (There’s a commercial from 3:15 to 4:22).

It’s about plants that disperse their seeds, spores, or pollen explosively, including liverworts, dogwoods, mosses, witch hazel, oats, and sundry others.

Not only do the explosions disperse the seeds (clearly an adaptive trait; you want your genes to be away from your plot, where they compete with you), but in some cases the explosion has evolved to give the dispersing seeds an orientation that makes them go further.  And some of the spores, as in horsetails, have little arms that curl with changes in humidity that allow them to “walk” along the ground! (Oat seeds can do the same thing, hopping with their “awns” and then twisting themselves into the ground.) As usual, the photography is amazing, so don’t miss this one. The extensive research is documented by a list of references at the end.

In this video ZeFrank doesn’t mention evolution or natural selection, but of course it’s implicit in these amazing and diverse adaptations for dispersal. I, for one, hardly knew anything about these features, and was delighted to see all these complicated results of natural selection, which of course is cleverer than you are.  Seeds that plant themselves by screwing themselves into the dirt!

h/t: Mary